A bicycle frame is the main component of a bicycle, on to which wheels and other components are fitted. The great majority of today's rigid-frame bicycles have a frame with upright seating. Such upright bicycles generally feature the diamond frame, a truss consisting of two triangles: the front triangle and the rear triangle. In a conventional diamond frame, the front “triangle” is not actually a triangle because it consists of four tubes: the head tube, top tube, down tube and seat tube. The head tube contains the headset, the set of bearings that allows the front fork (which supports the front wheel) to turn smoothly for steering and balance. The top tube connects the head tube to the seat tube at the top, and the down tube connects the head tube to the bottom bracket. The rear triangle consists of the seat tube and paired chain stays and paired seat stays. The chain stays run essentially parallel to the chain, connecting the bottom bracket to the rear fork ends (which support the rear wheel). The seat stays connect the top of the seat tube (at or near the same point as the top tube) to the rear fork ends.
Many modern bicycles do not utilize a diamond frame, for example because: the frame is constructed in such a way that it does not consist of tubes attached one to another (for example, frames made of composite materials); or the frame involves a rear suspension system permitting rearward components of the bicycle (e.g., the rear wheel) to move relative to other components of the bicycle (e.g., the seat); or both. However, the terms used to describe the members of a conventional diamond frame (being, head tube, top tube, down tube, seat tube, chain stays and seat stays) are often used to describe analogous features on non-diamond frames and are at times so used herein.
Most bicycles use a chain to transmit power to the rear wheel. The drivetrain begins with pedals which rotate the cranks, which are attached to a spindle that rotates within the bottom bracket. With a chaindrive, a chainring attached to a crank drives the chain, which in turn rotates the rear wheel via a rear sprocket. Most chaindrive systems have some form of gearing, typically comprising multiple rear sprockets of different sizes, multiple chainrings of different sizes and user controllable devices (referred to as derailleurs) for moving the chain between rear sprockets and between the chainrings, so as to selectively vary the gear ratio.
A bicycle suspension is the system or systems used to suspend the rider and all or part of the bicycle in order to protect them from the roughness of the terrain over which they travel. Bicycle suspensions are used primarily on mountain bikes, but are also common on hybrid bicycles, and can even be found on some road bicycles. Bicycle suspension can be implemented in a variety of ways, including: front-fork suspension and rear suspension. It is not uncommon for a mountain bike to have front suspension but no rear suspension (such a suspension configuration is often referred to as a hardtail). However, it is uncommon for a mountain bike to have a rear suspension system but no front suspension system. Thus, rear suspension systems on mountain bikes are typically part of a full suspension system.
Suspension systems for mountain bikes first appeared in roughly the early 1990's. Over the ensuing years developers and users of mountain bike suspension systems recognized a variety of factors affecting suspension performance and general riding performance of suspension system, which factors are interrelated in dynamic and complex ways. It was soon realized that the fact that bicycles are powered by human effort means that effects on the drive train caused by suspension system movement that would, in the case of engine driven vehicles, be minor or unnoticeable, are significant in bicycles. Early full suspension frames were heavy and tended to bounce up and down while a rider pedaled. This movement was called pedal bob, kickback, or monkey motion and reduced the efficiency of, or interfered with, a rider's pedal stroke—especially during climbs up steep hills. Input from hard braking efforts often also negatively affected the performance of early full suspension designs. When a rider hit the brakes (which often occurs in terrain situations in which the rear suspension is needed most), some early suspension designs tended to extend the shock (known as brake jack), causing a stiffening of the suspension, which tends to not allow the suspension to react to bumps very well. Some suspension designs exhibit brake squat, where braking forces tend to compress the suspension. This effect, in moderation, can be beneficial to counteract the normal forward weight transfer caused by braking.
In the field of bicycle suspension systems, the following terms are generally used as follows:                Travel refers to how much movement a suspension mechanism allows. It usually measures how much the wheel axle moves.        Bob and squat refer to how a suspension, usually rear, responds to rider pedalling. Squat usually refers to how the rear suspension compresses under acceleration, and bob refers to repeated squat and rebound with each pedal stroke. Both are undesirable characteristics as they rob power from pedalling.        Pedal feedback or chainstay lengthening refers to torque applied to the crankset by the chain caused by motion of the rear axle relative to the bottom bracket. Pedal feedback is caused by an increase in the distance between the chainring and rear sprocket, and it can be felt by the rider as a torque on the crankset in the rotational direction opposite to forward pedalling.        Preload refers to the force applied to spring component before external loads, such as rider weight, are applied. The amount of preload necessary depends on the rider weight and the parameters of the spring components. More preload makes the suspension sag less and less preload makes the suspension sag more. Adjusting preload affects the ride height of the suspension.        Rebound refers to the rate at which a suspension component returns to its original configuration after absorbing a shock. The term also generally refers to rebound damping or rebound damping adjustments on shocks, which vary the rebound speed. More rebound damping will cause the shock to return at a slower rate.        Sag refers to how much a suspension moves under just the static load of the rider. Sag is often used as one parameter when tuning a suspension for a rider. Spring preload is adjusted until the desired amount of sag is measured.        Lockout refers to a mechanism to disable a suspension mechanism to render it substantially rigid. This may be desirable during climbing or sprinting to prevent the suspension from absorbing power applied by the rider. Some lockout mechanisms also feature a “blow off” system that deactivates the lockout when an appropriate force is applied to help prevent damage to the shock and rider injury under high unexpected loads.        Compression damping refers to systems that slow the rate of compression in a front fork shock or rear shock. Compression damping is usually accomplished by forcing a hydraulic fluid (such as oil) through a valve when the shock becomes loaded. The amount of damping is determined by the resistance through the valve, a higher amount of damping resulting from greater resistance in the valve. Many shocks have compression damping adjustments which vary the resistance in the valve. Often, lockouts function by allowing no hydraulic fluid to flow through the compression damping valve.        Unsprung mass is the mass of the portions of bicycles that is not supported by the suspension systems.        
Numerous bicycle systems and variations of same are known. For example, as described in the following US patents:    U.S. Pat. No. 4,789,174, Suspension Bicycle, Lawwill, 6 Dec. 1988;    U.S. Pat. No. 5,121,937, Suspension Bicycle, Lawwill, 16 Jun. 1992;    U.S. Pat. No. 5,205,575, Cycle Rear Suspension System, Buell et al., 27 Apr. 1993;    U.S. Pat. No. 5,244,224, Rocker Arm Rear Suspension Bicycle, Busby, 14 Sep. 1993;    U.S. Pat. No. 5,441,292, Bicycle Rear Suspension System, Busby, 15 Aug. 1995;    U.S. Pat. No. 5,509,679, Rear Suspension For Bicycles, Leitner, 23 Apr. 1996;    U.S. Pat. No. 5,553,881, Bicycle Rear Suspension System, Klassen et al., 10 Sep. 1996;    U.S. Pat. No. 5,628,524, Bicycle Wheel Travel Path For Selectively Applying Chainstay Lengthening Effect And Apparatus For Providing Same, Klassen et al., 13 May 1997;    U.S. Pat. No. 5,899,480, Rear Suspension For Bicycles, Leitner, 4 May 1999;    U.S. Pat. No. 6,099,010, Bicycle With Crank Assembly Suspension System, Busby, 8 Aug. 2000;    U.S. Pat. No. 6,206,397, Bicycle Wheel Travel Path For Selectively Applying Chainstay Lengthening Effect And Apparatus For Providing Same, Klassen et al., 27 Mar. 2001;    U.S. Pat. No. 6,843,494, Rear Suspension System For Two-Wheeled Vehicles, Particularly Bicycles, Lam, 18 Jan. 2005;    U.S. Pat. No. 6,969,081, Bicycle Rear Suspension, Whyte, 29 Nov. 2005;    U.S. Pat. No. 7,048,292, Bicycle Suspension Systems, Weagle, 23 May 2006;    U.S. Pat. No. 7,066,481, Bicycle Rear Suspension, Soucek, 27 Jun. 2006;    U.S. Pat. No. 7,100,930, Bicycle Rear Suspension System, Saiki, 5 Sep. 2006;    U.S. Pat. No. 7,128,329, Vehicle Suspension Systems, Weagle, 31 Oct. 2006;    U.S. Pat. No. 7,240,912, Bicycle Rear Suspension, Whyte, 10 Jul. 2007;    U.S. Pat. No. 7,296,815, Bicycle Suspension Apparatus and Related Method, Ellsworth et al., 20 Nov. 2007;    U.S. Pat. No. 7,392,999, Bicycle With Rear Suspension, O'Connor, 1 Jul. 2008;    U.S. Pat. No. 7,494,146, Bicycle Frame, Tseng, 24 Feb. 2009;    U.S. Pat. No. 7,556,276, Bicycle Rear Wheel Suspension Chassis, Dunlap, 7 Jul. 2009;    U.S. Pat. No. 7,581,743, Bicycle Rear Wheel Suspension System With Controlled Variable Shock Rate, Graney, 1 Sep. 2009;    U.S. Pat. No. 7,635,141, Bicycle Rear Suspension System, O'Connor, 22 Dec. 2009;    U.S. Pat. No. 7,658,394, Rear Suspension Systems For Bicycles, Huang, 9 Feb. 2010;    U.S. Pat. No. 7,712,757, Suspension For Mountain Bicycles, Berthold, 11 May 2010;    U.S. Pat. No. 7,717,212, Vehicle Suspension Systems For Separated Acceleration Responses, Weagle, 18 May 2010;    U.S. Pat. No. 7,828,314, Vehicle Suspension Systems, Weagle, 9 Nov. 2010; and    U.S. Pat. No. 7,934,739, Bicycle Rear Suspension, Domahidy, 3 May 2011.
Further examples of bicycle systems and variations of same are described in the following US patent applications:    U.S. 2005/0057018, Bicycle Rear Suspension System, Saiki, 17 Mar. 2005;    U.S. 2008/0054595, Bicycle Frame With A Counter-Rotating Four Bar Linkage System; Lu, 6 Mar. 2008;    U.S. 2008/0067772, Vehicle Suspension Systems For Separated Acceleration Responses, Weagle, 20 Mar. 2008;    U.S. 2008/0217882, Two-Wheeled Vehicle With Rear Suspension, Beaulieu et al., 11 Sep. 2008;    U.S. 2008/0252040, Bicycle Rear Wheel Suspension System, Colegrove et al., 16 Oct. 2008;    U.S. 2008/0258425, Rear Fork For Bicycle, Tribotte, 23 Oct. 2008;    U.S. 2008/0277900, Bicycle With A Common Pivot Shock Absorber, I, 13 Nov. 2008;    U.S. 2009/0026728, Bicycle Rear Suspension, Domahidy, 29 Jan. 2009;    U.S. 2009/0072512, Bicycle Rear Suspension System, Earle, 19 Mar. 2009;    U.S. 2009/0261556, Bicycle Rear Suspension System Linkage, Beale, 22 Oct. 2009;    U.S. 2009/0283986, Rear Fork, Falke, 19 Nov. 2009;    U.S. 2010/0007113, Rear Suspension System For Bicycles, Earle et al., 14 Jan. 2010;    U.S. 2010/0059965, Bicycle Suspension System Employing Highly Predictable Pedalling Characteristics, Earle, 11 Mar. 2010;    U.S. 2010/0102531, Bicycle Rear Suspension System With Controlled Variable Shock Rate, Graney, 29 Apr. 2010;    U.S. 2010/0127473, Suspension Bicycle Derailleur Link, Cocalis et. al., 27 May 2010;    U.S. 2010/0156066, Mountain Bicycle Having Improved Frame Geometry, O'Connor, 24 Jun. 2010;    U.S. 2010/0327556, Bicycle Assembly With Rear Shock, Chamberlain, 30 Dec. 2010; and    U.S. 2011/0115181, Vehicle Suspension Systems, Weagle, 19 May 2011;